Blood glucose monitoring Flashcards
What is the normal concentration of blood glucose?
90mg per 100cm3
What monitors the concentration of blood glucose?
Cells in the pancreas
When does blood glucose rise?
After eating food containing carbohydrate
When does blood glucose fall?
After exercise as more glucose is used in respiration to release energy, when you’re stressed
What two hormones are used to control the concentration of blood glucose?
Insulin
Glucagon
What is a hormone?
A chemical messenger which travels in blood to their target cells
Where is insulin and glucagon secreted from?
Clusters of cells called islets of Langerhans
What cells do the Islets of Langerhans contain?
Alpha cells
Beta cells
Delta cells
What do beta cells secrete?
Insulin into the blood
What do alpha cells secrete?
Glucagon into the blood
What are insulin and glucagon examples of?
Effectors
What role does insulin play in controlling blood glucose concentrations?
Lowers blood glucose concentration when its too high
How does insulin affect cell membranes?
It binds to specific receptors on the cell membranes of muscle and liver cells, increasing the permeability to glucose so more is taken up. Done by increasing the number of channel proteins
What enzymes does insulin activate?
Muscle and liver cells that convert glucose into glycogen
What is glycogenesis?
The formation of glycogen from glucose
What does insulin increase the rate of?
Rate of respiration of glucose
What role does glucagon play in controlling blood glucose concentrations?
Raises blood glucose concentration when its too low
How does glucagon work?
It binds to specific receptors on the cell membranes of liver cells and activates enzymes that break down glycogen into glucose
What process does glucagon activate?
Glycogenolysis
What is glycogenolysis?
The formation of glucose from glycogen
What is gluconeogenesis?
The formation of glucose from non-carbohydrates such as amino acids and glycerol
What is a weakness of a hormonal response to control blood glucose?
It is slower than a nerve impulse response
What is a strength of a hormonal response to control blood glucose?
They are not broken down as quickly as neurotransmitters so effects last longer
Explain how negative feedback mechanisms respond to a rise in blood glucose concentration?
- When it is detected by the pancreas, the β cells secrete insulin and the α cells stop secreting glucagon
- Insulin binds to receptors on liver and muscle cells
- The liver and muscle cells respond to decrease the blood glucose concentration
- Glycogenesis is activated
- Blood glucose concentration returns to normal
Explain how negative feedback mechanisms respond to a fall in blood glucose concentration?
- When it is detected by the pancreas, the α cells secrete glucagon and the β cells stop secreting insulin
- Glucagon binds to receptors on liver cells
- Liver cells respond to increase the blood glucose concentration
- Glycogenolysis is activated
- Blood glucose concentration returns to normal
What are glucose transporters?
Channel proteins which allow glucose to be transported across a cell membrane
What type of glucose transporter is in skeletal and cardiac muscle cells?
GLUT4
What happens to glucose transporters when insulin levels are low?
GLUT4 is stored in vesicles in the cytoplasm but when insulin binds it triggers the movement of GLUT4 to the membrane. Glucose can then be transported into the cell by the protein by facilitated diffusion
What is adrenaline?
A hormone secreted from adrenal glands
When is adrenaline secreted?
When there’s a low concentration of glucose in your blood
What two things does adrenaline do?
Binds to receptors in the cell membranes of liver cells and;
- Activates glycogenolysis (breakdown of glycogen to glucose)
- Inhibits glycogenesis ( the synthesis of glycogen from glucose
What does adrenaline get the body ready for?
Making more glucose available for muscles to respire
What is the secondary messenger model?
The binding of the hormone to cell receptors activates an enzyme on the inside of the cell membrane, which they produces a chemical known as a second messenger
What does a secondary messenger do?
Activates other enzymes in the cell to bring about a response
How does adrenaline and glucagon act in terms of the secondary messenger model and activating glycogenolysis? (step by step)
- To activate glycogenolysis, adrenaline and glucagon bind to their receptors and activate an enzyme called adenylate cyclase.
- Activated adenylate cyclase converts ATP into a chemical called cyclic AMP (cAMP) which is a secondary messenger
- cAMP activates an enzyme called protein kinase A
- Protein kinase A activates a chain of reactions which breaks down glycogen into glucose
Why are glucagon and adrenaline receptors complimentary in shape to their respective hormones?
They have a specific tertiary structure
What is Diabetes Mellitus?
A condition that results in elevated blood glucose levels aka Hyperglycaemia.
Blood glucose continues to rise which then leads to progressive renal, nerve and ocular damage.
Diabetes is a major contributor to morbidity and mortality.
3 million adults have hyperglycaemia which makes up 5.9% of the population.
Outline what Type 1 diabetes is
10% of cases.
An autoimmune disease.
The destruction of insulin-secreting beta cells in pancreas which leads to no insulin therefore blood glucose continues to rise since the glucose can’t actually enter cells nor be metabolised for energy, so excess can’t be stored as glycogen. This can lead to body starting to burn fat and protein for energy.
Patients require daily insulin injections
Takes a day to die
Outline what Type 2 diabetes is
90% of cases.
Due to genetic and ethnic disposition and environmental, lifestyle factors- such as obesity and lack of exercise.
Cells become less responsive to insulin OR there is reduced insulin production by the pancreas.
Correlated with increasing age (Holt and Humar, 2015)
Individual may take meds to increase insulin production e.g injectable insulin.
Takes years to notice even have diabetes, and diee.
What is Gestational diabetes?
Due to onset of glucose intolerance during first onset of recognised pregnancy.
Increased chance of developing diabetes post-pregnancy. (Buchanan et al)
What are the different subtypes of diabetes?
- Idiopathic-no underlying autoimmune cause
- Endocrinopathies-diseases of endocrine glands aka Hormone problems.
- Drugs/chemical induced diabtes
What is a Glycaemic response?
changes in glucose level after absorption of carbohydrates (Maughan 2009; Sanders 2016)
Why is glucose monitoring important for diabetics?
- measurement is self care activity and positively correlates with glycaemic control (Shaji et al 2013; Shirastara et al 2013)
- measurement gives important info on effectiveness of blood glucose metabolism and guides interventions for optimal blood glucose control.
what are the normal blood glucose ranges and when should you start to monitor the patient?
How did we use to measure blood glucose and why did we change this method?
4.0-8.0 mmol litre
Fasting plasma glucose is 5-7 mmol litre
Used to use urine strips but accurate measurements rely on stable renal functions so are potentially unreliable (Holt, 2014)
what is hyperglycaemia?
what can happen after prolonged hyperglycaemia?
- This occurs when random plasma glucose of more than 11 mol/litre
- Prolonged hyperglycaemia can result in damage to many organs of the body leading to renal failure, blindness and gangrene (Boore et al, 2018)
what is acute hyperglycaemia? How can this lead to DKA?
- Acute hyperglycaemia happens when the body can’t use glucose due to insufficient/ complete lack of insulin production.
- This causes the body to generate glucose via glycogenolysis, lipolysis and gluconeogenesis.
- Blood glucose levels continue tor rise and then fatty acid metabolites AKA ketones accumulate leading to Ketoacidosis (DKA)
Hyperglycaemia can lead to hyperosmolar hyperglycaemic syndrome. What is this?
Blood glucose so high etc leads to severe dehydration and confusion
what are some Gastrointestinal symptoms for hyperglycaemia?
Nausea, vomiting, abdominal pain, hunger
what are some Andrenergic symptoms of hyperglycaemia?
fight or flight response
what are some respiratory symptoms for hyperglycaemia?
Glycosuria (excess glucose in urine), Polyuria (anmd dehydration) and Polydipsia (excess thirst)
what are some symptoms of hyperglycaemia due to electrolyte imbalance?
excess ketones from fast metabolism.
Hypokalaemia - too low potassium
Hyponatraemia- too low sodium
what are some symptoms of hyperglycaemia due to liver and andipose (body fat) tissue?
acetone breath
what are some cardiovascular symptoms to hyperglycaemia?
cardiac irregularities
what are some symptoms for the CNS due to hyperglycaemia?
CNS depression- drowsiness
coma
Outline what DKA is and how it can be identified:
- From severe hyperglycaemia
- Urine will test + for ketones and plasma ketones will be elevated
- Requires urgent hospital attention: insulin, fluid and K+ replacement and will require high intensity nursing in a critical care unit.
- This leads to electrolyte imbalance due to excessive acidosis so needs close monitoring of electrolytes.
- DKA could be presenting feature of newly diagnosed type 1 diabetes.
how is hyperosmolar in terms of mortality rate compared to DKA?
Is treatment any different?
- Higher mortality rate than DKA
- Management is similar but focuses more hydration and correction osmolality
what are the causes for hyperglycaemia?
- Inadequate doses on insulin
- Infection
- Stress
- Surgery
- Medications (steroids, benzodiazepines)
- Variations in nutritional intake
- Individual receiving eternal/parenteral feeding)
- critical illness
what is hypoglycaemia?
Plasma glucose level of below 4mmol/litre
Happens when blood glucose falls therefore inadequate energy to brain so abnormal behaviour like acting drunk
what are the causes for hypoglycaemia?
-Inadvertent insulin or sulphonylurea overdose ( sulph. increase endrogenous insulin prod in a person with type 2 diabetes)
- response to change in dose
- unexpected exercise
- error in timing of dosage
what is hypo-awareness?
Get so used to feeling tired that thresh hold gets higher and so might not even know that have hypoglycaemia until too late.
what are some symptoms for hypoglycaemia to do with the CNS?
- headache
- confusion
- concentration difficulties
- changes in personality
what are some cardiovascular symptoms for hypoglycaemia?
palpitations
what are some gastrointestinal symptoms for hypoglycaemia?
hunger, nausea, belching
what are some andrenergic symptoms for hypogycaemia?
sweating and anxiety
what are some treatments for mild-moderate hypoglycaemia?
1)10g sugar by mouth, repeat after 10-15 min and then give a snack (sustained carb release will minimise rebound)
OR
2)Give non-diet drink and 10g sugar
what are some treatments for severe hypoglycaemia?
- injection
- glucagon prescribed in an emergency
- give carb asap
- 20% glucose intravenous infusion
- Blood glucose should be monitored closely
- Type 1 may experience hypo-awareness
Describe the nursing process for taking blood glucose measurement:
1) wash hands
2) introduce
3) check patient details
4) Explain procedure
5) Gain consent
6) Ensure patient’s hands are clean- avoid wipes or alcohol
7) Gather equipment: blood glucose monitor, testing strips, lancet, gauze
8) Insert test strip into machine
9) put on gloves
10) Remove safety cap from lancet, warm finger and position on side of patients finger.
11) Pinch side of the finger
12) squeeze to prod blood drop
13) Touch tip of test strip against drop
14) Note reading
15) Dispose lancet and gloves
16) Thank patient
17) wash hands
18) Document blood glucose levels
